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funfun
03-22-2005, 08:35 PM
Does anyone know the implementation of fresnel()?
Thanks

shehbahn
03-22-2005, 09:08 PM
i don't remember the Renderman spec advocating a specific implementation for the Fresnel formula - if it's prman's that you are interested in, i don't think i can post that here, so i'll recommend :
- posting on the customer forum at www.pixar.com (in the renderman support area - requires registration)
- email rmancusp@pixar.com (they have answered that question before)

iirc you can also find a similar derivation in Glassner's books (principles of image synthesis)

funfun
03-22-2005, 09:48 PM
thanks shehbahn. Actually I want to write my own fresnel. I only know the basic fresnel function, but I have no idea how to return the refraction and reflection fractions (Kr, Kt) .

pgregory
03-23-2005, 07:46 AM
You could take a look at the Aqsis source code (http://www.aqsis.org). I can't remember where I sourced the implementation details from, I think it was a combination of web searching and reference books, but it seems to work ok.

Cheers

PaulG

mummey
03-23-2005, 01:38 PM
Hope this helps: http://www.rendermanacademy.com/docs/Fresnel.htm

shehbahn
03-23-2005, 07:36 PM
actually - there's one additional catch for your implementation not described in the spec iirc : total internal reflection returns a null vector and null kr

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